Audio Troubleshooting Continued

The audio problem still continues. The good news is that today I have a better troubleshooting plan, thanks to the AeroElectric list. The most frustrating thing about this problem was that I just didn’t have a good plan for how to isolate the problem. One list member suggested pulling all of the pins out of the connectors, and assembling them one circuit at a time to try and isolate the problem. First I removed all of the wires coming into the intercom except for the front left seat. That didn’t fix the problem. Next I used little alligator clip test leads to connect the left front seat input on the intercom directly to the headset plugs, bypassing the aircraft jacks. The problem was gone! I reconnected the airframe microphone jack on the front left, and the test was still good. I reconnected the audio jack on the front left, and the problem came back. A little bit of investigation led me to the problem- the audio jacks weren’t grounded. This happened through a series of events. First, our project’s previous owner had connected the audio jacks without any ground wires. He was planning to ground them through the airframe, as was I. While microphone jacks must not be grounded to the airframe, audio jacks can be. Some time later, I learned that while the audio jacks may be grounded via the airframe, it’s better if they are not. When I learned that, I drilled the holes to a larger diameter and installed insulating washers like the ones on the microphone jack. The only problem is that I didn’t come back after the fact to add a ground wire connection. The good news was that the shielded audio cable had an extra conductor available, so I was able to add the ground by shortening the cables a few inches on each end. It took me several hours to perform this soldering surgery, but as of the end of today it’s all ready to plug in and test. I’m just glad to have it figured out.

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Hours Logged This Session: 6.6
Total Hours: 1883.75

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